Related papers: Challenges to the Lambda CDM Cosmology
The conventional $\Lambda$CDM cosmological model supplemented by the inflation concept describes the Universe very well. However, there are still a few concerns: new Planck data impose constraints on the shape of the inflaton potential,…
The $\Lambda$CDM model is a remarkably successful model which is consistent with the observations of cosmic microwave background radiation (CMB), baryon acoustic oscillation (BAO), and large scale structure of the Universe. However, the…
We present logistic dark energy model (LDEM), where the dark energy density follows a logistic function for the scale factor. The equation of state parameter of dark energy ($w_D$) transitioned from $-1$ in the distant past to its current…
The cosmological constant $\Lambda$ and cold dark matter (CDM) model ($\Lambda\text{CDM}$) is one of the pillars of modern cosmology and is widely used as the de facto theoretical model by current and forthcoming surveys. As the nature of…
One of the most important problems vexing the $\Lambda$CDM cosmological model is the Hubble tension. It arises from the fact that measurements of the present value of the Hubble parameter performed with low-redshift quantities, e.g., the…
In this Thesis I discuss several recent results obtained using the CMB spectra measured by Planck and several other cosmological probes. Extensions of the $\Lambda$CDM model are studied, including the presence of an additional sterile…
The Hubble constant $H_0$ tension has emerged as the most serious crisis in modern cosmology, potentially indicating that the $\Lambda$CDM model may not describe our universe accurately. In this paper, we establish a new,…
We explore the bounds that can be placed on interactions between cold dark matter and vacuum energy, with equation of state $w=-1$, using state-of-the-art cosmological observations. We consider linear perturbations about a simple background…
The well-known tensions on the cosmological parameters $H_0$ and $\sigma_8$ within the $\Lambda$CDM cosmology shown by the Planck-CMB and LSS data are possibly due to the systematics in the data or our ignorance of some new physics beyond…
We explore an extended cosmological scenario where the dark matter is an admixture of cold and additional non-cold species. The mass and temperature of the non-cold dark matter particles are extracted from a number of cosmological…
We study the effect of an explicit interaction between two scalar fields components describing dark matter in the context of a recent proposal framework for interaction. We find that, even assuming a very small coupling, it is sufficient to…
In a previous work it was shown that by considering the quantum nature of the gravitational field mediator, it is possible to introduce the momentum energy of the graviton into the Einstein equations as an effective cosmological constant.…
Differences in the values of the Hubble constant obtained from the local universe and the early universe have resulted in a significant tension. This tension signifies that our understanding of cosmology (physical processes and/or…
The cosmic microwave background (CMB) comprises the oldest photons in the universe and is arguably our most direct cosmological observable. All precise and accurate measurements of its attributes serve to distinguish between cosmological…
A higher value of Hubble constant has been obtained from measurements with nearby Type Ia supernovae, than that obtained at much higher redshift. With the peculiar motions of their hosts, we find that the matter content at such low redshift…
The past, present and future of cosmic microwave background (CMB) anisotropy research is discussed, with emphasis on the Boomerang and Maxima balloon experiments. These data are combined with large scale structure (LSS) information and high…
We investigate a modified cosmological model aimed at addressing the Hubble tension, considering revised dynamics in the late Universe. The model introduces a parameter $c$ affecting the evolution equations, motivated by a modified Poisson…
Physics invites the idea that space contains energy whose gravitational effect approximates that of Einstein's cosmological constant, Lambda; nowadays the concept is termed dark energy or quintessence. Physics also suggests the dark energy…
Inflation provides a unified paradigm for understanding the isotropy of the cosmic microwave background (CMB), the flatness problem, and the origin of large-scale structure. Although the physics responsible for inflation is not yet well…
The dimming of Type Ia supernovae could be the result of Hubble-scale inhomogeneity in the matter and spatial curvature, rather than signaling the presence of a dark energy component. A key challenge for such models is to fit the detailed…